and precision, it is not less true that a careful
examination of apparently the simplest works of
creation will also reveal marvellous and unexpected
harmonies.

Milk is a white, non-transparent, homogeneous
fluid, heavier than water, of agreeable
and slightly sweetish flavour. If the milk betray
imperfect liquidity, it is not healthy milk, nor of
good quality. Its whiteness and non-transparency
are owing to its constitution. Milk,
in familiar terms, may be said to be composed of
four main ingredients; cream or butter, caseine
or cheese, lactine or sugar of milk associated
with other salts, and buttermilk or whey,
which forms the watery portion of its substance.
Seen under the microscope, it is found to be full
of globules of various sizes, which swarm in good
milk, are less abundant in poor milk, and are
still more numerous and large in cream. The
different appearances of good and of thin milk
are not unlike the different aspects of a slice
from a rich plum-pudding and a slice from an
economical one. It is these globules— the plums
and currants of the mixture— which give to
milk both its colour and its opacity. The greater
opaqueness of cream and the semi-transparency
of skimmed milk, or milk that has been liberally
watered, are a popular confirmation of the fact.
To see the globules in milk and the difference of
their size well, a high magnifying power (from
five to six hundred diameters) is desirable; but
they are perfectly and distinctly visible with a
good instrument magnifying from two hundred
to two hundred and fifty diameters.

The watery portion of milk possesses no
microscopic properties; nor are we aware that
there are microscopic means of distinguishing
the milk of one class of animals from that of
another, as there are of detecting different
bloods— the blood of reptiles, for instance, from
the blood of mammals. Each milk-globule consists
of fatty matter or butter, and is enveloped
in a thin coat of caseine, which prevents the
globules from melting into each other. If a
portion of a drop of milk be placed on a glass
slide for microscopic observation, and the thin
glass cover be rubbed to and fro with a certain
degree of pressure, the cheesy coating will be
ruptured, the globules of oil will run together,
and shreds of the coats, like broken egg-shells,
will be visible. If acetic acid be added to milk,
the coats will be acted upon, and the confluence
of the globules be also produced. The same
effect occurs naturally in sour milk, causing the
globules to be larger and more irregular in form
(frequently becoming elongated and united in
twos, so as to bear some resemblance to young
mushrooms) than they are in fresh milk.

Milk affords an interesting subject of study,
from its being the first aliment on which all
have, or ought to have, fed. Any deficiency in
its supply in infancy, is often felt through childhood,
youth, and even manhood. How can
growing babes make gristle and bone, if they do
not take in the proper materials to make them
with? Pap and arrowroot may be as palatable,
but they do not contain the same elements
milk. Milk suffices, alone and unaided, to maintain
and develop our bodily frame. A curious
problem, therefore, presents itself at the outset;
namely, to trace, in the composition of milk, the
composition of our bodily organs.

One of the least known, but also one of the
most indefatigable and conscientious authors who
have added fresh facts to the natural history of
milk, is the late M. Quevenne, who, in collaboration
with M. Bourchardat, published, in 1857,
an interesting work, Le Lait (Milk). During the
nineteen years he spent at the Hôpital de la
Charité, there were very few days on which he
did not make experiments to decide questions
relating to the composition of milk. From this
bland and apparently simple liquid, he extracted
no less than thirty-two different kinds of substances,
including water. The union of ten of
them constitutes butter. Four had been considered
as a single substance, known by the
name of caseum, or pure cheese. Amongst the
rest are lactine, sulphur, iodine, besides phosphates
of lime, magnesia, potash, iron, manganese,
and soda. Who would guess that such a
multitude of ingredients were to be found in a
glass of milk?

Nevertheless, by carefully searching out matters
which enter it only in very small quantities,
analysis promises still further discoveries. For
in this liquid, be it remembered, we ought to
find everything which exists in the human frame;
or at least everything which can give rise, by
admirable transformations, to the multitudinous
compounds of which the human frame is composed.

Food serves the double purpose, first of maintaining
vital heat in an animal, and, secondly, of
increasing its growth by the addition of fresh
substance to its various organs. In the latter
office may be included the repairing of losses and
injuries, as well as the accumulation of store
of flesh and fat. Heat-giving aliments are burnt
in the living human body, in such a way as to
produce a temperature of 37½° centigrade, or
99° and a fraction of Fahrenheit, which is consequently
called " blood heat." The result of the
combustion is water and carbonic acid, which
escape by the lungs. Every adult person, in
ordinary health, exhales more than two pounds
of carbonic acid in four-and-twenty hours. The
heat-giving aliments contained in good fresh
milk are lactine and butter.

Lactine is a white sugar, crackling, brittle,
scentless, slightly sweet, which may be procured
by the evaporation of skimmed milk. It is
called very properly sugar of milk; and it is
known that all sugars are not equally sweet to
the taste. Thus, cane sugar is sweeter than
beetroot sugar. It exists in eggs, and in the
milk of some, probably of all, carnivorous animals,
with whom its quantity is increased by
feeding them on bread. But what we know of
their milk is mainly derived from the sow and
the bitch; for few people would undertake the
task of milking a tigress or a lioness.

Cow's milk contains five per cent of lactine;
ass's milk, six and a half; woman's milk, seven